1. Field of the Invention
The present invention relates to a method of producing raw materials for activated carbon from petroleum heavy materials and, more particularly, it relates to a method of producing raw materials for activated carbon by the reaction of petroleum heavy materials such as petroleum heavy oils or petroleum heavy residues with a sulfonating agent.
2. Description of the Prior Art
Hitherto, raw materials for activated carbon have been produced by dry distilling in a fixed bed a woody carbonaceous material such as coconut shells and sawdust or a coal carbonaceous material at temperatures lower than about 600.degree.C. Then, the raw materials for activated carbon thus obtained are activated with an activating gas, such as a steam-containing gas and a carbon dioxide-containing gas, at temperatures of about 700.degree.C to about 1100.degree.C to provide activated carbon. On the other hand, when asphalt or a petroleum heavy material containing a large asphalt content is subjected to the aforesaid solid-bed dry distillation-activation step which is a conventional method of producing activated carbon, only activated carbon with a greatly inferior quality is obtained. Also, the so-called raw petroleum cokes, that is the heavy material obtained by subjecting a petroleum heavy material to low-temperature coking or cracking, only gives an activated carbon with a greatly inferior quality using an ordinary activation method. Furthermore, in the case of using those petroleum heavy materials as raw materials, the yield for the raw materials for activated carbon obtained by the dry distillation of them is as low as about 30% and further the activated carbon obtained from such raw materials for activated carbon is low in bulk density and is brittle.
As a method of overcoming the disadvantages of the above-mentioned method, an improved method of producing activated carbon from a petroleum heavy material is disclosed in the specification of U.S. Pat. No. 2,809,938, in which asphalt is treated with concentrated sulfuric acid, the product is carbonized by dry distilling the product at about 500.degree.C in the absence of oxygen to remove substantially all unreacted sulfuric acid and volatile matter, and then the carbonized product is activated at a high temperature using an activating gas. The method of the aforesaid patent may be excellent in that a practically useful activated carbon can be produced using petroleum heavy materials as raw materials but since the method requires a dry distillation and carbonization steps, from the standpoint of the amount of heat required, it is economically disadvantageous and further the activated carbon produced only has properties inferior to the properties of commercially available conventional activated carbon. The reason that the properties of the activated carbon produced by the method of the above-cited U.S. Pat. No. 2,809,938 is believed to be as follows: That is, in the method the structure of the material to be converted into a porous material in the subsequent activation step is damaged in the dry distillation step for removing the volatile matter.
Also, in the specification of Japanese patent publication No. 6818/56, a method is described for producing activated carbon by dry distilling the sulfuric acid sludge or sulfuric acid pitch produced as by-products in the refining of oils with sulfuric acid at temperatures of 500.degree.-700.degree.C while introducing steam to the system to remove substantially all of the volatile matter and then activating the product with an activating gas. The Japanese Patent specification also teaches that since sulfuric acid pitch contains a large amount of impurities containing actively deleterious materials, an activated carbon of good quality cannot be obtained without dry distilling the sulfuric acid pitch at 500.degree.-700.degree.C while introducing steam into the system for removing those actively deleterious materials and that if the temperature for the dry distillation is lower than 500.degree.C or higher than 700.degree.C, a high quality activated carbon is not obtained. Thus, this method requires a dry distillation step as a necessary factor and hence is economically disadvantageous from the standpoint of the heat required, and further the activated carbon produced only has the same properties as those of commercially available activated carbon.
Also, in "Hydrocarbon Processing", January, 105-108 (1971), a method is described of producing activated carbon by impregnating raw petroleum coke with a mixture of sulfuric acid and phosphoric acid but from the experimental results described in the report, the properties of the activated carbon produced by the method are inferior to those of commercially available activated carbon.